JP2016203400A - THERMAL RECORDER MANUFACTURING METHOD, THERMAL RECORDER MANUFACTURING DEVICE, AND THERMAL RECORDER - Google Patents

Abstract

The present invention provides a method for producing a thermal recording material, which can produce a stable thermal recording material by forming a curtain-like film that is more stable than conventional ones. A multilayer thin film having three or more layers is formed by coatings Sa, Sb, and Sc discharged from three or more slits 5a, 5b, and 5c, including a thermal coating for forming a thermal layer that develops color when heated. Then, when coating is performed by dropping onto the continuously running long base material 21, the dynamic surface tension of the paint Sa forming the outermost layer in the falling state is determined by the coating Sb of the layer adjacent to the outermost layer. Less than or equal to the dynamic surface tension in the fall state. [Selection] Figure 1

Description

  The present invention relates to a method for producing a thermal recording material. The present invention also relates to a thermal recording medium manufacturing apparatus and a thermal recording medium.

  As a method for producing a heat-sensitive recording material, there is a coating with a curtain coater. By applying multiple layers simultaneously using a curtain coater, it is possible to manufacture a thermosensitive recording body in which multiple layers are laminated in a fewer number of steps compared to the conventional manufacturing method of laminating one layer at a time. There are many advantages, such as being able to make the interface between the layers easy to strengthen.

  In order to produce a heat-sensitive recording material with a curtain coater, it is necessary to control the paint into a curtain-like film during coating. Here, the heat-sensitive coating for forming the heat-sensitive recording layer is a suspension in which a solid material such as a dye or a developer is dispersed in a solution. The nature is low. Therefore, a technique for stabilizing the curtain film has been developed. Non-Patent Document 1 describes that in a curtain coater using a slide die, the dynamic surface tension of the lower layer is slightly higher (a few mN / m) than the dynamic surface tension of the upper layer. Has been. Patent Document 1 describes a technique for suppressing the generation of defects in which paint does not adhere to an ellipse or streamline by controlling the dynamic surface tension between layers during simultaneous multilayer coating.

LIQUlD FILM COATING Stephan F. Kistler and Peter M. SchweiZer CHAPMAN & HALL

JP 2010-240640 A

  However, according to the knowledge of the applicant, “the difference in dynamic surface tension (A−B) between the thermal surface tension B of the coating of the heat-sensitive recording layer and the adjacent layer is 4 mN / m or less (cited document 1 [claimed Even in the case of item 1]), the curtain film is not sufficiently stable, liquid cracking, neck-in, etc. may occur, and coating may become unstable.

  The present invention has been made for the purpose of solving the above-mentioned problems, and the object thereof is to produce a stable thermal recording material by forming a curtain-like film that is more stable than conventional ones. An object of the present invention is to provide a method for producing a thermosensitive recording material.

  (1) The production method of the present invention forms a multilayer thin film of three or more layers by a plurality of paints each ejected from three or more slits, including a heat sensitive paint for forming a heat sensitive layer that develops color by heating. This is a method for producing a heat-sensitive recording material, wherein the plurality of coating materials are applied onto the base material by dropping it onto a long base material that runs continuously. The method for producing a thermal recording medium, wherein the dynamic surface tension of the coating material forming the outermost layer of the multilayer thin film in a falling state is not more than the dynamic surface tension of the layer adjacent to the outermost layer in the falling state of the coating material. It is.

  According to the above configuration, since the dynamic surface tension of the paint forming the outermost layer is lower than the dynamic surface tension of the adjacent layer, that is, the immediately inner layer, in the fall state, the outermost layer paint has an interface between the adjacent layers. It is easy to spread to cover. Since the same applies to the outermost layer on the opposite side, the falling multilayer film is covered from both sides, and the multilayer film is stabilized.

  (2) The production apparatus of the present invention forms a multilayer thin film of three or more layers by a plurality of paints each ejected from three or more slits, including a heat sensitive paint for forming a heat sensitive layer that develops color by heating. The apparatus for manufacturing a heat-sensitive recording material, wherein the plurality of coating materials are applied onto the base material by being dropped onto a long base material that continuously runs. The apparatus for producing a thermal recording body, wherein the dynamic surface tension of the coating material forming the outermost layer of the multilayer thin film in a falling state is equal to or less than the dynamic surface tension of the layer adjacent to the outermost layer in the falling state of the coating material. It is.

  According to the above configuration, since the dynamic surface tension of the paint forming the outermost layer is lower than the dynamic surface tension of the adjacent layer, that is, the immediately inner layer, in the fall state, the outermost layer paint has an interface between the adjacent layers. It is easy to spread to cover. Since the same applies to the outermost layer on the opposite side, the falling multilayer film is covered from both sides, and the multilayer film is stabilized.

  (3) It is preferable that the manufacturing method or manufacturing apparatus of this invention is applied so that the layer formed with the heat-sensitive paint may contact the said base material.

  According to this structure, a heat sensitive layer is laminated | stacked on the lowest layer side among all the layers coated simultaneously. Therefore, it is possible to easily manufacture a heat-sensitive recording material that protects the heat-sensitive layer with another layer.

  (4) Since the thermal recording material produced by the production method or production apparatus of the present invention is produced by coating by dropping a stable multilayer film, the coated layer is uniformly formed. It tends to be a heat-sensitive recording material.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the thermosensitive recording body which can manufacture the thermosensitive recording body stable by forming a curtain-like film | membrane stable compared with the past, and the manufacturing apparatus which applied the manufacturing method In addition, it is possible to provide a thermal recording body manufactured by applying the manufacturing method or the manufacturing apparatus.

FIG. 1 is a schematic configuration diagram of a curtain coater. FIG. 2 is a schematic configuration diagram of the curtain coater as viewed from the front. FIG. 3 is a diagram illustrating a method for measuring dynamic surface tension, and is a schematic configuration diagram of a curtain coater as viewed from the front.

  In the following, referring to FIGS. 1 to 3, an embodiment of a manufacturing method to which the manufacturing method of the thermal recording material of the present invention is applied and a curtain coater which is a manufacturing apparatus to which the thermal recording material of the present invention is applied will be described. Using the curtain coater, a heat-sensitive recording body having a three-layer structure having a heat-sensitive recording layer, a protective layer, and a surface layer on a substrate is produced by a simultaneous multilayer coating curtain coating method. In the following description, directions and directions follow the arrows and descriptions in the drawings.

  FIG. 1 is a schematic configuration diagram of a curtain coater used for the simultaneous multilayer coating. The curtain coater includes a slide die 1, and the slide die 1 has a slide inclined surface 3 that is inclined downward on its upper surface. The slide inclined surface 3 is provided with slits 5a to 5c for discharging paints Sa to Sc for forming the respective layers of the thermal recording body.

  On the upstream side of the slits 5a to 5c, paint reservoirs 7a to 7c are provided to stabilize the discharge of the paints Sa to Sc. Paint supply pipes 9a to 9c are connected to the lower ends of the slits 5a to 5c, and the paints Sa to Sc are supplied to the paint supply pipes 9a to 9c by pumps 10a to 10c respectively provided in the paint supply pipes 9a to 9c. It is supplied to the paint reservoirs 7a to 7c through 9c.

  Among the coating materials Sa to Sc, the thermal coating material Sc is a coating material used for forming a thermal recording layer that develops color when heated, and is similar to the conventional thermal recording layer forming coating material including a color former, a developer, a binder, and the like. It is a dispersion liquid. The protective coating Sb is a coating used for forming a protective layer for protecting the thermosensitive recording layer, and is an aqueous solution or emulsion mainly composed of a resin as in the conventional case. The surface coating Sa is a coating used for forming a surface layer laminated on the surface of the heat-sensitive recording material, and is a dispersion in which various components such as pigments are contained in a solvent, as in the past.

  Among the slits 5a to 5c, the slit 5a that discharges the surface paint Sa is at the rearmost, and the slit 5b and the slit 5c are arranged in order toward the front. The discharged paints Sa to Sc flow forward on the slide inclined surface 3 while forming the paint layers 17a to 17c. Moreover, since all of the coating materials Sa to Sc are discharged upward from below, the discharged liquid discharged at the front forms a coating layer below the flowing liquid that is discharged at the rear and forms a coating layer. More specifically, the protective coating layer 17b formed by the protective coating Sb discharged from the slit 5b sinks below the surface coating layer 17a formed by the surface coating Sa discharged from the slit 5a behind the slit 5b. Formed as follows. Similarly, the heat-sensitive paint layer 17c formed by the heat-sensitive paint Sc discharged from the slit 5c in front of the slit 5b is formed so as to sink under the protective paint layer 17b. As a result, on the slide inclined surface 3, the heat-sensitive paint layer 17 c, the protective paint layer 17 b, and the surface paint layer 17 a are sequentially formed on the slide inclined surface 3 in the state of forming a laminated film in this order from below. go.

  The front end portion of the slide inclined surface 3 is provided with a tip portion called a lip 13 having a slope that curves downward as it goes forward. By passing through the lip 13, the laminated film forms a curtain coating film 19 as shown in FIG.

  An edge guide 15 extends downward from the left and right ends in the width direction of the lip 13 downward. Accordingly, the left and right end portions of the curtain coating film 19 are guided by coming into contact with the edge guide 15 and fall downward while maintaining the curtain shape.

  As shown in FIG. 1, the long base material 21 is continuously supplied from the rear to the front and the surface upward. Since the lower end portion of the curtain coating film 19 reaches the base material 21, the coating layer 17 a is bent in such a manner that the lower end portion of the curtain coating film 19 is bent forward as the base material 21 moves forward. ˜17c is coated on the substrate 21. Specifically, the coating layers 17a to 17c are formed from the lower layer side in the order of the thermal layer formed by the thermal coating Sc, the protective layer formed by the protective coating Sb, and the surface layer formed by the surface coating Sa. 21 is laminated. Then, a thermal recording body is manufactured through a drying process.

  By the way, since the coating materials Sa to Sc have surface tension, the laminated film on the slide inclined surface 3 receives a force in a direction of decreasing the surface area. As a result, the laminated film may shrink in the width direction or the film thickness may become unbalanced. Here, since it is the surface coating layer 17a that is the uppermost layer that has an interface with the outside air on the slide inclined surface 3, the surface tension is the most problematic because of the surface coating Sa that forms the surface coating layer 17a. Is the surface tension. That is, in order to stabilize the laminated film on the slide inclined surface 3, it is effective to reduce the surface tension of the surface coating Sa. Since the laminated film is moving forward on the slide inclined surface 3, the problem here is not the static surface tension but the dynamic surface tension at the moving speed.

  On the other hand, if the dynamic surface tensions of both layers in contact with each other in the laminated film are extremely different, the interface between the two layers is not stable. Therefore, for example, the dynamic surface tension of the surface paint Sa is preferably close to the dynamic surface tension of the protective paint Sb. That is, the dynamic surface tension of the protective coating Sb is preferably equal to or slightly larger than the dynamic surface tension of the surface coating Sa. Since the same can be said for the relationship between the protective paint Sb and the thermal paint Sc, the dynamic surface tension increases in the order of the surface paint Sa, the protective paint Sb, and the thermal paint Sc, that is, in order from the upper layer to the lower layer. It is preferable to become. Such consideration has already been made in Non-Patent Document 1, and it is claimed in Patent Document 1 that the same can be said for a solution containing a heat-sensitive paint.

  On the other hand, in the state where the curtain coating film 19 is formed and freely falls downward, not only the uppermost surface coating layer 17a but also the lowermost thermal coating layer 17c has an interface with the outside air. That is, it is important that the dynamic surface tension of the surface paint layer 17a and the heat-sensitive paint layer 17c, which are the outermost layers when a curtain-like multilayer thin film is formed and dropped, is small. In addition, since the other conditions are not different from those of the laminated film on the slide inclined surface 3 described above, the dynamic surface tension of the protective coating Sb is the largest, and the dynamic surface tension of the surface coating Sa and the thermal coating Sc that forms the outermost layer. Is preferably equal to or smaller than the dynamic surface tension of the protective coating Sb.

  Thus, the preferable dynamic surface tension relationship in the laminated film on the slide inclined surface 3 does not coincide with the preferable dynamic surface tension relationship in the curtain coating film 19 during free fall. Further, since the transition from the laminated film to the curtain coating film 19 is performed instantaneously and continuously by passing through the lip 13, the two dynamic surface tension relations are moved during the process so that both are preferable. It is difficult to change the surface tension.

  Let's consider that. As described above, only the upper surface contacts the outside air on the slide inclined surface 3. On the other hand, in the curtain coating film 19, both the front surface and the rear surface are in contact with the outside air. That is, the influence of the surface tension is increased as compared with the laminated film on the slide inclined surface 3. In addition, the laminated film on the slide inclined surface 3 moves at a substantially constant speed, whereas the curtain coating film 19 has an acceleration movement due to free fall. Accordingly, the film thickness easily changes and becomes unstable. Specifically, a neck-in in which the lower part of the curtain coating film 19 becomes thinner than the upper part and a film crack in which the curtain coating film 19 is separated into two or more films are likely to occur. Accordingly, importance is attached to the stability of the curtain coating film 19, and the dynamic surface tension of the surface coating Sa and the thermal coating Sc is the same as or smaller than the dynamic surface tension of the protective coating Sb. This is important for suppressing the occurrence of engineering defects. Therefore, in the present embodiment, the components of the paints Sa to Sc are adjusted using a surfactant or the like so that the dynamic surface tension of the paint Sa and the paint Sc is equal to or less than the dynamic surface tension of the paint Sb. Note that, as described above, although the coating conditions of Patent Document 1 are applied, the curtain-shaped film does not have sufficient stability, neck-in or film cracking occurs, or curtain coating from the edge guide. The film may come off. In addition, coating defects may be seen on the coated web. These are considered to be because the dynamic surface tension of Sc was larger than that of the paint Sb.

In order to adjust the coating material so that the above-described dynamic surface tension relationship is actually obtained, it is essential to measure the dynamic surface tension. Non-Patent Document 1 describes a method of directly measuring the actual dynamic surface tension of a falling curtain coating film. Specifically, as shown in FIG. 3, a portion of the surface of the curtain coating film is split by slightly contacting the tip of the needle P with the surface of the curtain coating film, and the following (1) The dynamic surface tension can be measured by the equation.
Here, σ is the dynamic surface tension, ρ is the liquid density, Q is the flow rate per unit width, and V is the film speed at the point where the needle P contacts. The split angle α is an angle formed between the end of the film generated by splitting and the vertical direction. At this time, when the entire curtain coating film is separated by piercing the needle P deeply into the curtain coating film, the dynamic surface tension cannot be measured accurately.

  According to the present embodiment described above, the following effects can be obtained.

  According to the present embodiment, the dynamic surface tension of the surface paint Sa and the heat-sensitive paint Sc that forms the outermost layer in the falling state of the dynamic surface tension is the dynamic surface tension of the protective paint Sb that is a layer adjacent to the outermost layer. Since it is below the surface tension, it contributes to the stability of the curtain coating film 19.

  In addition, you may change the said embodiment as follows.

  In the above embodiment, the curtain coater is provided with the edge guide 15 but is not essential. Since the edge guide 15 suppresses the neck-in by guiding the end of the curtain film, if the neck-in can be prevented by adjusting the dynamic surface tension or other conditions, the edge guide 15 is omitted. May be.

  In the above embodiment, the curtain coating film 19 is formed via the slide die 1. However, the curtain coating film 19 is formed by dropping the coating materials Sa to Sc directly downward from the slits 5 a to 5 c. You may apply about a curtain coater.

  In the above embodiment, the three-layer film of the paint layers 17a to 17c made of the paint Sa to Sc is formed, but a multilayer film of four or more layers may be used. Even in such a case, the same effect can be obtained by making the dynamic surface tension in the falling state of the coating material forming the outermost layer of the multilayer film equal to or less than the dynamic surface tension in the falling state of the coating material in the layer adjacent to the outermost layer. Is obtained.

  In addition, it is a matter of course that the method for manufacturing a thermal recording body, the manufacturing apparatus for the thermal recording body, and the thermal recording body may be configured in different modes within the scope of the claims.

  Examples of the present invention will be described below.

[Adjustment of paint]
○ Adjustment of thermal paint.
As shown in Table 1, a thermal dye dispersion, a thermal developer dispersion, an inorganic pigment dispersion, latex and water were mixed to prepare three types of thermal paints of formulas 1 to 3. Moreover, latex and water were mixed to prepare a comparative solution having no heat sensitive component. Hereinafter, unless otherwise specified, all numerical units are wet parts by weight.

In the table, “pigment content” indicates wet parts by weight of the solid component in the thermal dye dispersion, thermal developer dispersion, and inorganic pigment dispersion. Therefore, it is not contained in the comparison liquid.

○ Adjustment of protective paint.
Adjustment was made by adding 25.0 parts by weight of water to 75.0 parts by weight of the acrylic resin.

○ Adjustment of surface paint.
30.0 parts by weight of water was added to 20.0 parts by weight of the acrylic resin and 50.0 parts by weight of the inorganic pigment dispersion to prepare.

[Adjustment of viscosity]
The viscosity was adjusted to 400 cps for all of the discharged liquid. For the adjustment, completely saponified PVA was used.

[Coating conditions]
Using a slide die type curtain coater adjusted to a curtain coating width of 1000 mm and a curtain height of 100 mm, the above-mentioned heat-sensitive paint, protective paint and surface paint were simultaneously applied in multiple layers. Each coating flow rate is as follows.
Thermal paint: 0.4cc / (cm · sec)
Protective paint: 0.3cc / (cm · sec)
Surface paint: 0.3cc / (cm · sec)

[Experiment 1]
Using Formula 1 as the thermal paint, add acetylene glycol surfactant to each solution so that the surface tension of the thermal paint, protective paint and surface paint is 30mN / m, 35mN / m and 30mN / m, respectively. The adjusted liquid was applied under the above conditions, and the state of the curtain coating film was evaluated.

[Experiment 2]
Coating was performed in the same manner as in Experiment 1 except that Formula 2 was used as the heat-sensitive paint, and the state of the curtain coating film was evaluated.

[Experiment 3]
Coating was performed in the same manner as in Experiment 1 except that Formula 3 was used for the heat-sensitive paint, and the state of the curtain coating film was evaluated.

[Experiment 4]
Coating was performed in the same manner as in Experiment 1 except that the comparative liquid was used for the heat-sensitive paint, and the state of the curtain coating film was evaluated.

[Experiment 5]
Using Formula 1 as the thermal paint, add acetylene glycol surfactant to each liquid so that the surface tension of the thermal paint / protective paint / surface paint is 35 mN / m, 35 mN / m, and 30 mN / m, respectively. The adjusted liquid was applied under the above conditions, and the state of the curtain coating film was evaluated.

[Experiment 6]
Coating was performed in the same manner as in Experiment 5 except that Formula 2 was used for the heat-sensitive paint, and the state of the curtain coating film was evaluated.

[Experiment 7]
Coating was performed in the same manner as in Experiment 5 except that Formula 3 was used for the heat-sensitive paint, and the state of the curtain coating film was evaluated.

[Experiment 8]
Using Formula 1 as the thermal paint, add acetylene glycol surfactant to each solution so that the surface tension of the thermal paint, protective paint, and surface paint is 40 mN / m, 35 mN / m, and 30 mN / m, respectively. The adjusted liquid was applied under the above conditions, and the state of the curtain coating film was evaluated.

[Experiment 9]
Coating was performed in the same manner as in Experiment 8 except that Formula 2 was used as the heat-sensitive paint, and the state of the curtain coating film was evaluated.

[Experiment 10]
Coating was performed in the same manner as in Experiment 8 except that Formula 3 was used for the heat-sensitive paint, and the state of the curtain coating film was evaluated.

[Experiment 11]
Coating was performed in the same manner as in Experiment 8 except that the comparison liquid was used for the heat-sensitive paint, and the state of the curtain coating film was evaluated.

[Experiment 12]
Using Formula 1 as the thermal paint, add an acetylene glycol surfactant to each solution so that the surface tension of the thermal paint, protective paint, and surface paint is 40 mN / m, 35 mN / m, and 40 mN / m, respectively. The adjusted liquid was applied under the above conditions, and the state of the curtain coating film was evaluated.

[Experiment 13]
Coating was performed in the same manner as in Experiment 12 except that Formula 2 was used for the heat-sensitive paint, and the state of the curtain coating film was evaluated.

[Experiment 14]
Coating was performed in the same manner as in Experiment 12 except that Formula 3 was used for the heat-sensitive paint, and the state of the curtain coating film was evaluated.

The results of Experiment 1 to Experiment 14 are shown in Table 2.

Here, the state of the curtain coating film was evaluated as follows.
○: Good.
Δ: Stability near the edge guide is poor.
X: along the edge guide is bad.

[Evaluation]
Judging from the results of Experiments 1 to 4, when the dynamic surface tension of the middle layer is maximized, that is, the dynamic surface tension in the falling state of the paint is the dynamic surface in the falling state of the paint of the layer adjacent to the outermost layer. When the tension is smaller than the tension, the curtain coating film is stable regardless of whether the heat-sensitive paint is a suspension (Experiments 1 to 3) or a solution (Experiment 4). Next, judging from the results of Experiments 5 to 7, when the dynamic surface tension of the thermal coating and the dynamic surface tension of the protective coating as the adjacent layer are the same, the vicinity of the edge guide is increased when the pigment component is increased. However, it does not lead to cracking of the coating film. Therefore, from the results of Experiments 1 to 7, the thermal recording in which the dynamic surface tension in the falling state of the paint forming the outermost layer of the multilayer thin film is equal to or less than the dynamic surface tension in the falling state of the paint in the layer adjacent to the outermost layer. Regardless of whether it is a suspension or a solution, it can be confirmed that the body is an effective method for producing a thermal recording body.

  On the other hand, judging from the results of Experiments 8 to 11, when the dynamic surface tension is decreased in order from the lower layer side, the solution (experiment 11) does not contain a pigment component, that is, an insoluble solid component in the thermal paint. A stable coating film is formed. However, when the pigment content is included, the stability is deteriorated (Experiments 8 and 9), and when the pigment content is large, coating cannot be performed (Experiment 10). Therefore, it can be confirmed that the conventional method for producing a thermal recording material does not provide a sufficient effect on the suspension.

  Judging from the results of Experiments 12 to 14, when the dynamic surface tension of the middle layer is the smallest, that is, the dynamic surface tension in the fall state of the outermost layer paint is the fall state of the paint layer in the layer adjacent to the outermost layer. Obviously, the curtain coating is most unstable when the dynamic surface tension is greater than.

DESCRIPTION OF SYMBOLS 1 ... Slide die 3 ... Sliding inclined surface 5a, 5b, 5c ... Slit 9a, 9b, 9c ... Paint supply pipe 10a, 10b, 10c ... Pump 13 ... Lip 15 ... Edge guide 17a ... Surface paint layer 17b ... Protective paint layer 17c ... thermal paint layer 19 ... curtain coating film 21 ... base material P ... needle Sa ... surface paint Sb ... protective paint Sc ... thermal paint α ... split angle

Claims (4)

A long substrate that continuously runs by forming a multilayer thin film of three or more layers by a plurality of paints each discharged from three or more slits, including a heat-sensitive paint for forming a heat-sensitive layer that develops color by heating A method for producing a thermal recording material, wherein the plurality of coating materials are applied onto the substrate by dropping the coating material on the substrate,
A method for producing a thermal recording material, wherein a dynamic surface tension of the coating material forming the outermost layer of the multilayer thin film in a falling state is equal to or less than a dynamic surface tension of the layer adjacent to the outermost layer in the falling state of the coating material. A long substrate that continuously runs by forming a multilayer thin film of three or more layers by a plurality of paints each discharged from three or more slits, including a heat-sensitive paint for forming a heat-sensitive layer that develops color by heating An apparatus for producing a thermal recording body, wherein the plurality of coating materials are applied onto the base material by dropping it on the substrate,
An apparatus for producing a thermal recording medium, wherein a dynamic surface tension of the coating material forming the outermost layer of the multilayer thin film in a falling state is equal to or less than a dynamic surface tension of the layer adjacent to the outermost layer in the falling state of the coating material.   The manufacturing method of Claim 1 or the manufacturing apparatus of Claim 2 with which the layer formed with the said heat-sensitive coating material is applied so that the said base material may be contact | connected.   A heat-sensitive recording material to which the paint is applied by the production method or the production apparatus according to claim 1.